The invention relates to a backlight module, and in particular to a backlight module employed in a 2-D/3-D display device.
Currently, some display devices provide both 2-D and 3-D display capabilities. FIG. 1 shows a conventional 2-D/3-D display device. The display device 1 comprises a display panel 10, a 2-D/3-D switching panel 11, and a backlight module 12. The backlight module 12 provides light of equal brightness in both 2-D and 3-D display modes.
Referring to FIG. 2, when the display panel 10 displays an image with a 2-D display mode, the 2-D/3-D switching panel 11 is a totally pervious area TA, so that, light from the backlight module 12 can be fully transmitted to the display panel 10. Both eyes of a user see the same image, and the image is recombined and is perceived as a flat image in user's brain. The flat image is called a 2-D image.
Referring FIG. 3, when the display panel 10 displays an image in 3-D display mode, the 2-D/3-D switching panel 11 comprises a plurality of black areas BA with a barrier and a plurality of pervious areas TA. The black areas BA of the 2-D/3-D switching panel 11 block part of the light emitted from the backlight module 12. The right and left eyes of a user see different images due the linearity of light. In FIG. 3, “R” represents the image on the display panel 10 seen by the right eye watches, and “L” represents the image on the display panel 10 seen by the left eye watches. The different images seen by the right and left eyes are recombined and perceived as a 3-D image.
Since the black areas BA of the 2-D/3-D switching panel 11 block part of light from the backlight module 12 when the display panel 10 displays an image in a 3-D display mode, light received by the display panel 10 is reduced. Compared with a 2-D display mode, a 3-D image is darker than a 2-D image. Thus, when the display device 10 is switched from 2-D display mode to 3-D display mode, the image brightness changes.